1. Field of the Invention
The present invention relates generally to olefin polymerization catalysts and preparation methods, and more particularly, to olefin polymerization catalysts having high polymerization activities and a method of preparing such catalysts.
2. Description of the Prior Art
The production of sodium-free silica by hydrolyzing a silicate ester in an organic solvent under conditions such that only one phase is present is known. Further, it is known to introduce a transition metal compound into the silica containing solution and to cogel the silica and transition metal compound to form a catalyst. For example, U.S. Pat. No. 4,301,034 issued Nov. 17, 1981 discloses a process for producing sodium-free silica by the hydrolysis of a silicate ester and forming a transition metal catalyst therewith. The process basically comprises hydrolyzing a silicate ester in the presence of an organic solvent in which the ester and resulting silica are soluble. In order to catalyze the hydrolysis reaction, a strong mineral acid such as sulfuric acid is added to the reactant solution. A transition metal compound is subsequently added to the solution followed by the addition of a gelling agent whereby a catalyst comprised of gelled silica and transition metal oxide is formed.
By the present invention, an improved hydrolysis method is provided for preparing polymerization catalysts whereby the addition of an acid to the hydrolysis solution for catalyzing the hydrolysis reaction is obviated and the catalysts produced have high polymerization activities.